Review Question - QID 908

Flexion and extension gaps during TKA must be balanced to provide a knee that is stable throughout its range of motion. Changes to the tibia, such as modifying the size of the polyethylene insert, affect both the flexion gap and the extension gap. Conversely, changes to the femur typically affect either the flexion gap or the extension gap, but not both. Moving the femoral component anterior or posterior increases or decreases the flexion gap respectively. In a similar manner, moving the femoral component proximally or distally increases or decreases the extension gap respectively. In this question, the patient is loose in flexion and stable in extension. This can be addressed by either moving the femoral component posterior, or upsizing the femoral component which will only increase the AP diameter of the prosthesis. Therefore, answer 1 is correct.

Whiteside et al is a review article that discusses the proper techniques that results in a knee that is balanced to varus and valgus stresses in flexion and extension.